.\"	$NetBSD: usleep.3,v 1.19 2010/04/29 17:29:56 jruoho Exp $
.\"
.\" Copyright (c) 1986, 1991, 1993
.\"	The Regents of the University of California.  All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. Neither the name of the University nor the names of its contributors
.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\"     @(#)usleep.3	8.1 (Berkeley) 6/4/93
.\"
.Dd April 29, 2010
.Dt USLEEP 3
.Os
.Sh NAME
.Nm usleep
.Nd suspend execution for interval of microseconds
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In unistd.h
.Ft int
.Fn usleep "useconds_t microseconds"
.Sh DESCRIPTION
The
.Fn usleep
function
suspends execution of the calling process
until either the number of microseconds specified by
.Fa microseconds
have elapsed or a signal is delivered to the calling process and its
action is to invoke a signal catching function or to terminate the
process.
The suspension time may be longer than requested due to the
scheduling of other activity by the system.
.Pp
The
.Fa microseconds
argument must be less than 1,000,000.
If the value of
.Fa microseconds
is 0, then the call has no effect.
.Sh RETURN VALUES
On successful completion,
.Fn usleep
returns 0.
Otherwise, it returns \-1 and sets
.Va errno
to indicate the error.
.Sh ERRORS
The
.Fn usleep
function may fail if:
.Bl -tag -width Er
.It Bq Er EINVAL
The
.Fa microseconds
interval specified 1,000,000 or more microseconds.
.El
.Sh SEE ALSO
.Xr nanosleep 2 ,
.Xr sleep 3
.Sh STANDARDS
The
.Fn usleep
function conforms to
.St -xpg4.2 .
It later appeared in the
.Tn POSIX
standard, but in
.St -p1003.1-2004
it was marked as legacy and the use of
.Xr nanosleep 2
was recommended instead.
The
.St -p1003.1-2008
revision removed
.Fn usleep
from the specification.
.Sh HISTORY
The
.Fn usleep
function appeared in
.Bx 4.3 .
